One more violation will result in termination of their rental agreement.Study roommate agreements and strengthen your rules.

Two completely unrelated exceptions to the general rule.2.

Given you have $200k-$225k in equity in your townhouse in Clayton, NC, this could serve as a substantial down payment for one or more new properties.Rehab: If the properties you purchase need updates or repairs, invest in making those improvements.

Your city should have enforcement rules that require him to maintain his property in a manner that prevents damage to your property.If the city doesn't help, then you can try paying for it yourself and sending him the bill.

Is there a generic rule anyone follows that tends to work? 

Set clear house rules, take lots of pics, and communicate like crazy.

Are there any rules preventing me from asking about their pet?

They chose to refinance at 70 LTV to keep their cashflow higher, which meant that their new loan was 164K and they took out their initial downpayment + close to 30K additional... leaving no money in the deal with a deal that still fit the 1% rule and cash flowed.

Another benefit is that the OR Coast is a second home area which can often improve lending and mortgage terms. 

What does it take to be succesful and then get that what it takes and then attempt being succesful.If it takes you $3K, a car, and 100 hours /week, that is what it takes.I didn't make the rules.